Why is back-probing a sensor important?
Back-probing allows us to see how a sensor operates in real-time. In other words, it give’s “eyes” to see a sensor’s behavior as it tries to carry out it’s job. You’ll need a multimeter to carry out this test.
So how do I back-probe a sensor?
Connectors are exactly what they sound like; they connect the wiring harness to a component. In order to protect against the elements, connectors have rubber insulators where the wire enters into the connector. Our goal is to slip a small piece of metal in between the insulator and the wire. This is where we introduce one of the most important tools sensor diagnostics: The Paper Clip.
– Disclaimer- The paper clip is exposed metal, so be careful when using it with live voltage sources. Grounding battery voltage can lead to harm. For best results and safety, use the appropriate probes for your voltmeter (links at the bottom of the page).
The paper clip is perfect for going in between the insulation and the wire, is conductive, and they are easy to find. Simply insert the paper clip as show below. It will take a little work, but you should feel the paper clip rest against the bottom of the wire inside the connector.
The finished product should look similar to the pictures below.
Once this step is complete, it’s easy to connect the leads of your multimeter to the paper clips. The idea of back-probing a sensor is one of the basic skills that is used through out this site.